The invention relates to an apparatus for metallurgically heat treating workpieces, and more particularly, to a method and apparatus for surface treating workpieces.
Surface treating (e.g. carburization and carbonitriding) of metal (e.g. steel) workpieces is well-known wherein the composition of the workpieces for a certain depth from the surface (of the workpieces) is altered. This alteration may give the workpieces various properties. An example is when a steel workpiece is carburized, a "case" of increased carbon content is formed at and below the surface so that the workpiece may be hardened upon being quenched.
In the past, the surface treating of metals utilize a chamber into which passes a conduit. A reactive atmosphere is introduced into the chamber through the conduit. For the most part, a gross excess volume of reactive atmosphere is introduced into the chamber so that a complete surface reaction will occur. However, the consequences of introducing an excess of reactive atmosphere sometimes is to cause some components of the reactive atmosphere to precipitate out. Carbon precipitation not only causes the workpieces to become "dirty", but also contaminates and shortens the operating life of the chamber. Further, the introduction of a gross excess volume of reactive atmosphere is wasteful.
Thus, it would be highly desirable to provide an apparatus for metallurgically surface treating workpieces which would only require a volume of the reactive atmosphere that approximates the theoretical volume required for the reaction. It would also be highly desirable to provide an apparatus for metallurgically surface treating workpieces which would not cause the workpieces to become "dirty". It would also be highly desirable to provide an apparatus for metallurgically surface treating workpieces which is not wasteful of the reactive atmosphere and which does not shorten the life of the chamber.
Using presently existing methods and apparatus, the reactive atmosphere is not forcefully introduced into the chamber so as to facilitate the exposure of the workpieces to the reactive atmosphere. Only the mechanical jostling of the workpieces exposes them to the reactive atmosphere within the chamber. Few attempts have been made to better expose the workpieces to the reactive atmosphere. Thus, it would be highly desirable to provide an apparatus for metallurgically surface treating workpieces which includes means for facilitating the exposure of the workpieces to the reactive atmosphere other than mechanical jostling. It would also be highly desirable to provide an apparatus for metallurgically surface treating workpieces that includes the forceful distribution of the reactive atmosphere directly into the workpieces contained within the chamber.
Using existing methods and apparatus, the reactive atmosphere is allowed to freely flow through and out of the chamber. No attempt has been made to provide a means to impede this free flow. By dividing the treating chamber into a plurality of atmospherically isolated reaction chambers, less reaction gas can be used, and better control of the concentration of reaction gas can be achieved. Thus, it would be highly desirable to provide an apparatus for metallurgically surface treating workpieces that divides the treating chamber into a plurality of atmospherically isolated reaction chambers and prevents the free flow of reactive atmosphere through the chamber.